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[v2,3/4] iommu/vt-d: Do not enable ATS for untrusted devices

Message ID 20181126111526.56340-4-mika.westerberg@linux.intel.com
State Changes Requested
Delegated to: Bjorn Helgaas
Headers show
Series PCI / iommu / thunderbolt: IOMMU based DMA protection | expand

Commit Message

Mika Westerberg Nov. 26, 2018, 11:15 a.m. UTC 
Currently Linux automatically enables ATS (Address Translation Service)
for any device that supports it (and IOMMU is turned on). ATS is used to
accelerate DMA access as the device can cache translations locally so
there is no need to do full translation on IOMMU side. However, as
pointed out in [1] ATS can be used to bypass IOMMU based security
completely by simply sending PCIe read/write transaction with AT
(Address Translation) field set to "translated".

To mitigate this modify the Intel IOMMU code so that it does not enable
ATS for any device that is marked as being untrusted. In case this turns
out to cause performance issues we may selectively allow ATS based on
user decision but currently use big hammer and disable it completely to
be on the safe side.

[1] https://www.repository.cam.ac.uk/handle/1810/274352

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Ashok Raj <ashok.raj@intel.com>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/intel-iommu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 76e135ee9b19..c964315deddd 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1473,7 +1473,8 @@  static void iommu_enable_dev_iotlb(struct device_domain_info *info)
 	if (info->pri_supported && !pci_reset_pri(pdev) && !pci_enable_pri(pdev, 32))
 		info->pri_enabled = 1;
 #endif
-	if (info->ats_supported && !pci_enable_ats(pdev, VTD_PAGE_SHIFT)) {
+	if (!pdev->is_untrusted && info->ats_supported &&
+	    !pci_enable_ats(pdev, VTD_PAGE_SHIFT)) {
 		info->ats_enabled = 1;
 		domain_update_iotlb(info->domain);
 		info->ats_qdep = pci_ats_queue_depth(pdev);